A few quick, interesting facts about a different topic each entry. It's like an apple a day: pleasant, good to have, and pocket-sized.

Monday, January 12, 2009

Apple #363: The Purpose of Mosquitoes

Last week, a friend told me about a story he'd heard on NPR, about how mosquitoes alter the pitch of the whine they make in order to harmonize with and woo a potential mate. This is a very cool bit of information, but the fact that it was about mosquitoes raised that old question for us, what good are mosquitoes anyway?

Bite us and inject us with their saliva, to which we are allergic and which makes us itch

Carry terrible diseases like

Malaria

Yellow fever

Dengue fever

West Nile virus

Lyme disease

Encephalitis

In dogs, heartworm

By the way, only female mosquitoes bite. Male mosquitoes don't have the proboscis for it. They also don't need the blood. The females need blood only a few days out of their lifecycle, just before they're going to lay their eggs.

But what are the good things they do?

Mosquitoes and especially their larvae are food for fish, birds, frogs, bats, etc. But mosquitoes make up only about 1% of the diet of other animals and insects. Some scientists will even say that if you removed mosquitoes from the planet, those animals wouldn't starve because they eat lots of other stuff besides mosquitoes.

But, the scientists caution, you don't really want to get rid of all mosquitoes from the planet because they might play a bigger role than we realize. So, okay, I ask, what role could that be?

In addition to themselves being a food source, they pollinate. Nectar is their food (not blood), so when they stick their long skinny noses into the plants to get after the nectar, they also happen to collect and distribute pollen.

The don't pollinate a lot of plants, but some, including:

Certain grasses

Some species of Platanthera orchids

Goldenrod

The Platanthera flava, or the pale-green orchid, and one of the plants pollinated by mosquitoes as well as other insects. This species is threatened or endangered in its home locales.(Photo from Robert W. Freckmann Herbarium at U of Wisconsin)

In all of those above cases, mosquitoes are not the only pollinators to visit those plants. For example, some species of orchids are pollinated by mosquitoes and also butterflies. Both have really long noses that they can stick way down into the orchid to get at the nectar, and in the process, get pollen all over themselves. So you could also make the argument that, even when it comes to pollination, if you got rid of all the mosquitoes in the world, the impact wouldn't be that great.

However, there is one plant that is pollinated only by mosquitoes. It is the blunt-leaved bog orchid, (Habenaria or Platanthera obtusata). It grows in bogs and other swampy or wet woody places. Most people seem to talk about it growing in northern Wisconsin, but its habitat is in wetlands all over the Northeast, Midwest, and lower Canada. Varieties also grow in Alaska and Eurasia.

Platanthera obtusata, or bog-leaved orchid, here blooming in Colorado. This plant, too, is threatened and likely to become endangered in the foreseeable future.(Photo from SW Colorado Wildflowers)

So the question then becomes, what role does this plant play in the greater scheme of things? I haven't found anybody who has the answer to that, or at least they're not giving it out for free on this here Internet. But as you've probably learned elsewhere by now, wetlands play very important roles in cleaning fresh water and balancing other ecosystems like forests and and aquifers. All the plants in a wetland -- and the species diversity in a wetland environment is quite vast -- play important parts in keeping the wetland healthy and functioning.

So even though I can't tell you exactly what the Platanthera obtusata's role is in the world of wetlands, I'm going to bet that it does support other organisms in some crucial way. So if we want to preserve this and other bog orchids, it looks like we're going to have to keep the mosquito.

That said, I'm not saying, "Let's all love the mosquitoes," and don't slap them if they're biting you. Because in addition to being annoying, they do spread horrific and nasty diseases that kill people. Maybe there's a way we can manage them better, without killing lots of other stuff in the process, or maybe there's a way we can get them to stop carrying around those diseases. I mean, talk about baggage.

So, hey, scientists, would you get on that, please? Thanks.

Here are some other tidbits I came across while researching mosquitoes:

Pesticides that are used to kill mosquitoes are also in some cases killing honeybees. (This is not the primary reason for the rash of colony collapses that are devastating the honeybee population, however. [edit 2012: actually it's beginning to look as though pesticides may be the culprit in colony collapse, after all.])

Because there are fewer honeybees, other types of flying insects -- the kind most of us don't like, such as flies, midges, and mosquitoes -- are now becoming the dominant pollinators in some countries.

Cacao trees, the source of chocolate, are pollinated only by biting midges and gall midges.

I mean, it's our fault that they bite us so much. If that plant was not endangered, they would have more nectar, and not need our blood. It is partly our fault. Or the fault of whatever is killing that plant, and in some other universally interconnected way, our fault, too- probably.

Thank you for the information, I had just seen something on the Dirty Jobs television program about mosquitoes serving some important purpose, but when I wanted to sound so impressive with the knowledge, all I could come up with was food for the animals. But you gave me much more info to tell my co-workers tomorrow.:O)

Much like bees and their important role in the pollinating of flowers, I have a theory that sees Mosquitoes performing a critical role towards our continued survival on the planet.

The basis of my theory is built on the premise that the mosquito may be a kind of “real time sampler” transferring tiny samples of various organisms and foreign bodies between different species in order to keep those species immune systems alert and active to their ever changing environments. What is a mosquito but a flying syringe anyway?

It may be for the purpose of allowing for the various species immune systems to, in a way, study and analyse these foreign bodies in order to best get a learned jump on them.

If there were no mosquitoes, it may well be that the immune systems of many species on earth would become over worked through forever being “surprised”, thus eventually leading to that species ultimate extinction.

If science were to one day genetically bring back to life a woolly mammoth from past ages, it has been suggested that it would not survive that long, as its antiquated immune system could not possibly cope with the current day’s environment and the various bugs that exist. To use an analogy, it’s like a personal computer with an out of date antivirus system, chances are that it won’t be too long until the computer will freeze and crash. And how does science intend to bring back the woolly mammoth anyway? By utilising a small sample of the mammoth’s DNA which has been miraculously preserved in the fossilised mosquitoes of its day.

It could well be that the mosquito is not just an annoying disease spreading pest, but an unpaid and highly unappreciated laboratory worker. The mosquito could be playing a vital role in an extremely delicate balancing act which sees various organisms learning to “live and learn from one another” towards the common goal of continuing to exist on the planet.

The Human Immune System

The simplest reaction of the immune system is for example that triggered by a mosquito bite: an inflammation. When the insect has bitten, the immune system sends cell groups that do not have any special defensive skill. These cells, mostly neutrophils, travel along the blood flow tracking non-familiar chemical trails. When they find them, they release chemical signals asking for new forces, that agglomerate to kill the invader. This is like an infantry attack.

If the invaders are too powerful for this first line of defense, the immune system sends a second wave of cells, the innate immune cells. These cells are programmed with biochemical weapons that can attack a specific type of invaders, including the most common viruses, like cold or gripe viruses.

Sometimes, this is not enough and sometimes the immune system appeals to the most specialized cells of the immune system that learn from experience. Once exposed to a virus or bacteria, they recognize it if it appears again. That's why if you already have had smallpox for example, it's not likely you will get it again.

It's estimated that mosquitoes have killed 45 billion people over the course of human history and you're talking about how they can benefit orchids?! I say wipe them off the face of the earth with DDT!

You make a cogent point. My point was not to say, oh, that orchid is so precious so let's protect it at all costs. My point is, mosquitoes do apparently serve some purpose. And as we have learned again and again, when you mess with a relationship among species, you almost always create some sort of unintended consequence that is often worse than the current situation. Who knows, if we go messing around with mosquitoes on some drastic scale, what other problem we might create as a result?

This is ESPECIALLY true if you're serious about using DDT. I hope you're joking about that because the use of DDT led to the widespread sickening and near-extinction of several species of birds, bald eagles chief among them. In addition, while DDT has been said to be less harmful to humans than to birds and other animals, recent research is suggesting otherwise, that it does cause tumors in the liver and kidney, and it does interfere with fertility in humans, and it can lead to genetic mutations at the chromosomal level. (see http://newsinfo.iu.edu/news/page/normal/11583.html and http://pmep.cce.cornell.edu/profiles/extoxnet/carbaryl-dicrotophos/ddt-ext.html)

In fact, the use of DDT is often cited as one of the prime examples of negative unintended consequences (see for example http://en.wikipedia.org/wiki/Unintended_consequences#Unintended_consequences_of_environmental_intervention).

In sum, I don't mean to suggest that the deaths of 45 billion people are inconsequential and that we should do nothing to try to save people's lives in the future. But I do think we ought to be very careful about how we go about approaching problems lest we cause others.

How interesting -- all of you. I just got back from a silent retreat at a monastery. As I was walking in the gardens of an evening, contributing my precious blood to thirsty egg-baring insects, I wondered why God made the lowly mosquito? It couldn't have been just for bat food. Bats eat other things. I was "in to" deep pondering (you would be, too, after 3 days of silence!) and tried hard to think of one good thing a mosquito did for the world. It kept me up that night. THANK YOU, THANK YOU, dear bloggers for teaching me that they are pollinators. Who knew?

Did Jesus and the apostles swat and kill mosquitos when they bit them? I know this may be hard to rationalize, but we are also part of the ecosystem people. And if we decide to destroy the mosquito or any other specie then our act is also part of nature.Have a great day, Mark Sanford

You know, you're right, I sometimes forget that we're part of the ecosystem!

I don't mean that we shouldn't swat a mosquito when it lands on us. What I'm talking about is some large-scale, wholesale plan to eliminate them. After having made such an attempt, we would almost certainly discover some equally large-scale, wholesale consequence that we had never anticipated, one which may be just as bad as the current situation, or worse.

I tell you... the Apple Lady's right. If we did some day manage to wipe out all the mosquitoes, we may well find ourselves very sorry that we did... as we don't fully understand what their actually purpose is and where they may fit in to the grand scheme of things. I had a theory a few years back which I posted on this board (see it up the top there somewhere)... I'm pretty certain that if it's not right... it's definitely in the ball park somewhere.

Dear All,No doubt mosquitoes are beneficial in certain way of the eco system, HOWEVER, we should maintain that eradication programme for both malaria's & dengue's vectors shall bring more good than bad. Other mosquitoes if they do not create any problem for us, it is OK to let them live far in those remote areas..... AIK (all insect killer), Malaysia

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